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.TH ENDHOSTENT 3XNET "Nov 1, 2003"
.SH NAME
endhostent, gethostbyaddr, gethostbyname, gethostent, sethostent \- network
host database functions
.SH SYNOPSIS
.LP
.nf
\fBcc\fR [ \fIflag\fR ... ] \fIfile\fR ... \fB-lxnet\fR [ \fIlibrary\fR ... ]
#include <netdb.h>
extern int h_errno;

\fBvoid\fR \fBendhostent\fR(void)
.fi

.LP
.nf
\fBstruct hostent *\fR\fBgethostbyaddr\fR(\fBconst void *\fR\fIaddr\fR, \fBsocklen_t\fR \fIlen\fR, \fBint\fR \fItype\fR);
.fi

.LP
.nf
\fBstruct hostent *\fR\fBgethostbyname\fR(\fBconst char *\fR\fIname\fR);
.fi

.LP
.nf
\fBstruct hostent *\fR\fBgethostent\fR(void)
.fi

.LP
.nf
\fBvoid\fR \fBsethostent\fR(\fBint\fR \fIstayopen\fR);
.fi

.SH DESCRIPTION
.sp
.LP
The \fBgethostent()\fR, \fBgethostbyaddr()\fR, and \fBgethostbyname()\fR
functions each return a pointer to a \fBhostent\fR structure, the members of
which contain the fields of an entry in the network host database.
.sp
.LP
The \fBgethostent()\fR function reads the next entry of the database, opening a
connection to the database if necessary.
.sp
.LP
The \fBgethostbyaddr()\fR function searches the database and finds an entry
which matches the address family specified by the \fBtype\fR argument and which
matches the address pointed to by the \fIaddr\fR argument,  opening a
connection to the database if necessary.  The \fIaddr\fR argument is a pointer
to the binary-format (that is, not null-terminated) address in network byte
order, whose length is specified by the \fIlen\fR argument.  The datatype of
the address depends on the address family.  For an address of type
\fBAF_INET\fR, this is an \fBin_addr\fR structure, defined in
<\fBnetinet/in.h\fR>. For an address of type \fBAF_INET6\fR, there is an
\fBin6_addr\fR structure defined in <\fBnetinet/in.h\fR>.
.sp
.LP
The \fBgethostbyname()\fR function searches the database and finds an entry
which matches the host name specified by the \fIname\fR argument, opening a
connection to the database if necessary. If  \fIname\fR is an alias for a valid
host name, the function returns information about the host name  to which the
alias refers, and  \fIname\fR is included in the list of aliases returned.
.sp
.LP
The \fBsethostent()\fR function opens a connection to the network host
database, and sets the position of the next entry to the first entry.  If the
\fIstayopen\fR argument is non-zero, the connection to the host database will
not be closed after each call to \fBgethostent()\fR (either directly, or
indirectly through one of the other \fBgethost*(\|)\fR functions).
.sp
.LP
The \fBendhostent()\fR function closes the connection to the database.
.SH USAGE
.sp
.LP
The \fBgethostent()\fR, \fBgethostbyaddr()\fR, and \fBgethostbyname()\fR
functions may return pointers to static data, which may be overwritten by
subsequent calls to any of these functions.
.sp
.LP
These functions are generally used with the Internet address family.
.SH RETURN VALUES
.sp
.LP
On successful completion, \fBgethostbyaddr()\fR, \fBgethostbyname()\fR and
\fBgethostent()\fR return a pointer to a \fBhostent\fR structure if the
requested entry was found, and a null pointer if the end of the database was
reached or the requested entry was not found.  Otherwise, a null pointer is
returned.
.sp
.LP
On unsuccessful completion, \fBgethostbyaddr()\fR and \fBgethostbyname()\fR
functions set \fIh_errno\fR to indicate the error.
.SH ERRORS
.sp
.LP
No errors are defined for \fBendhostent()\fR, \fBgethostent()\fR and
\fBsethostent()\fR.
.sp
.LP
The \fBgethostbyaddr()\fR and \fBgethostbyname()\fR functions will fail in the
following cases, setting \fIh_errno\fR to the value shown in the list below.
Any changes to \fBerrno\fR are unspecified.
.sp
.ne 2
.na
\fB\fBHOST_NOT_FOUND\fR\fR
.ad
.RS 18n
No such host is known.
.RE

.sp
.ne 2
.na
\fB\fBNO_DATA\fR\fR
.ad
.RS 18n
The server recognised the request and the name but no address is available.
Another type of request to the name server for the domain might return an
answer.
.RE

.sp
.ne 2
.na
\fB\fBNO_RECOVERY\fR\fR
.ad
.RS 18n
An unexpected server failure occurred which can not be recovered.
.RE

.sp
.ne 2
.na
\fB\fBTRY_AGAIN\fR\fR
.ad
.RS 18n
A temporary and possibly transient error occurred, such as a failure of a
server to respond.
.RE

.SH ATTRIBUTES
.sp
.LP
See \fBattributes\fR(7) for descriptions of the following attributes:
.sp

.sp
.TS
box;
c | c
l | l .
ATTRIBUTE TYPE	ATTRIBUTE VALUE
_
Interface Stability	Standard
_
MT-Level	MT-Safe
.TE

.SH SEE ALSO
.sp
.LP
.BR endservent (3XNET),
.BR htonl (3XNET),
.BR inet_addr (3XNET),
.BR attributes (7),
.BR standards (7)
